The invention relates to implants for humans or animals. The implants at least partly create positive-fit connections to human or animal tissue parts, particularly skeletal parts, wherein the implants help connect tissue parts together, or help connect tissue parts to means supporting or replacing tissue parts, or to other therapeutic auxiliary devices. The invention further relates to methods for implanting implants into humans or animals.
Known implants for creating connections to skeletal parts (bones) include screws, pins, etc., which are used for connecting bones to bones, or bones to artificial, carrying, stabilizing, or supporting parts, or to parts replacing skeletal parts (stabilization or fixation plates, sutures, wires, artificial joint elements, artificial teeth, etc.). Such connection elements for implantation consist for example of metal or plastic, including resorbable plastic. After healing, the connection elements are removed by a further operation or they are left in the body where they are possibly gradually decomposed and replaced by vital tissue.
For stabilizing a bone fracture, a fixation plate with suitable holes is fixed in the region of the fracture using screws as mentioned above. Plate and screws may consist of metal (e.g. stainless steel or titanium). The screws are self-cutting and are rotated into threadless openings in the bone, or they are screwed into pre-drilled threaded openings. Pins are inserted into previously created openings for similar purposes. Connections created in the foregoing manner are usually based on frictional engagement, possibly on positive fit.
It is known also to use curable, plastic materials (e.g. particular cements on a hydraulic or polymer base) for creating connections of the mentioned type. Such materials are pressed from the outside between implant and vital tissue, or into tissue defects in a highly viscous condition, and are cured in situ. Positive-fit connections can be created using such material, if the openings into which the material is pressed comprise suitable undercuts. In order to reduce the stress and/or costs of the corresponding operation method so-called biodegradable implants, e.g. bone pins are used. That is, bone pins which degrade over time and which are then absorbed by the body. One of such known biodegradable bone pins is known under the trademark Polypin. This bone pin consists of a polyactid-copolymer mixture and is absorbed during a period of about two years. The attachment of such resorbable polymer pins to bone is done by press fitting such pins into a predrilled hole in a bone.
Also known in the art is the usage of thermoplastic polymer materials which can be liquefied in a targeted manner by way of mechanical oscillation and, in this condition, can be pressed into cavities by way of hydrostatic pressure, thereby creating positive fit connections after solidification.
Furthermore, from U.S.2005/0249773 the importance of bone replacement materials is known, in particular in the areas of orthopedics, traumatology, cranial, dental and facial surgery, and orthodontics continues to increase. Significant areas of application for bone implants include, for example, the closing of large bone defects associated with comminuted fractures as well as the attachment of small bone fragments, the filling of bone defects resulting from bone cysts and after removal of bone tumors, the filling of voids caused by chronic osteomyelitis, applications associated with material loss on alveolis and jaw bones and the use as a carrier material, for example, for antibiotics, cytostatic, and osteogenic materials.
In most cases, bone defects can be treated by the insertion of bone augmentation materials. Healing is promoted if the implants closely contact the surrounding bone walls. Thus, it is advantageous to be able to form a bone implant in a particular shape. For instance, if a tooth is extracted, the bone implant used to fill the void preferably nearly replicates the tooth root. Improperly shaped bone implants can lead to problems such as soft tissue ingrowth and poor adhesion between the implant and existing bone. In addition, improper shape can lead to complications or patient discomfort.
Properly shaping a bone implant is often very challenging. In some cases the repair site is deep within the body and covered by soft tissue and body fluids. In other cases, such as with a tooth extraction, the root of the extracted tooth can be used to make a mold. However, even when repairing a tooth extraction wound, there are times when the root is broken into pieces and not available for molding. In other situations, the bone implant must be molded after it has been placed in the injury site.
According to U.S.2005/0249773 the above-mentioned problems are overcome by providing an osteoconductive and/or osteoinductive biocompatible implant composition that that can be readily molded in-situ or ex-situ into a desired shape. Once the moldable implant composition is formed into a desired shape, the implant composition is easily, and if desired, quickly hardened to form a rigid implant. Such an implant composition may forms an open porous scaffolding or composite matrix that allows in-growth and/or regeneration of bone tissue. In another version, the solvent is included in an amount sufficient to form a liquid implant that can be poured or injected into an implant site.